Trimodally porous SnO₂ nanospheres with threedimensional interconnectivity and size tunability: A one-pot synthetic route and potential application as an extremely sensitive ethanol detector

The rapid and effective transfer of chemical reactants to solid surfaces through porous structures is essential for enhancing the performance of nanomaterials for various energy and environmental applications. In this paper, we report a facile one-pot spray pyrolysis method for preparing highly reactant-accessible and porous SnO₂ spheres, which have three-dimensionally interconnected and size-tunable trimodal (microscale, mesoscale and macroscale) pores. For this synthetic method, macroscale polystyrene spheres and mesoscale-diameter, long carbon nanotubes were used as sacrificial templates. The promising potential of the SnO₂ spheres with trimodal pores (sizes ∼3, 20 and 100 nm) was demonstrated by the unprecedentedly high response to several p.p.b. levels of ethanol. Such an ultrahigh response to ethanol is explained with respect to the hierarchical porosity and pore-size-dependent gas diffusion mechanism.